The nuclear winter theory also remains controversial, with some scientists saying the predicted effects have been exaggerated.

核冬天理论也受到了质疑，有些科学家认为预测的结果被夸大了。

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The theory behind outdoor napping is that children exposed to fresh air, whether in summer or the depths of winter, are less likely to catch coughs and colds - and that spending a whole day in one room with 30 other children does them no good at all.

BBC: The babies who nap in sub-zero temperatures